Electronic apparatus

ABSTRACT

According to an embodiment, an electronic apparatus includes a printed circuit board including a plurality of devices that include a nonvolatile memory package and a controller package configured to control the nonvolatile memory package, and a housing accommodating the printed circuit board. The housing includes an opening on a surface constituting the housing. An encryption device among the plurality of devices is present in a first region. The first region is a region on the printed circuit board that is not irradiated with light emitted from a light source placed at the opening. The encryption device is a device used for an encryption process of data to be stored into the nonvolatile memory package.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims benefit under 35 U.S.C.§ 120 to U.S. application Ser. No. 17/660,075 filed Apr. 21, 2022, whichis a continuation of and claims benefit under 35 U.S.C. § 120 to U.S.application Ser. No. 17/120,982 filed Dec. 14, 2020, which is acontinuation of and claims benefit under 35 U.S.C. § 120 to U.S.application Ser. No. 16/662,558, filed Oct. 24, 2019, which is acontinuation of and claims benefit under 35 U.S.C. § 120 to U.S.application Ser. No. 15/824,125, filed Nov. 28, 2017, which is basedupon and claims the benefit of priority under 35 U.S.C. § 119 fromJapanese Patent Application No. 2017-031040, filed Feb. 22, 2017, andbased upon and claims the benefit of priority under 35 U.S.C. § 119 fromJapanese Patent Application No. 2017-149384, filed Aug. 1, 2017, theentire contents of each of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an electronicapparatus.

BACKGROUND

An electronic apparatus is known in which a housing accommodates boardswith packages mounted thereon and the packages contain a nonvolatilesemiconductor memory and a controller for controlling the nonvolatilememory. In this electronic apparatus, a base or cover constituting thehousing is provided with openings for attaching and detachingconnectors.

In the case of the conventional structure, the packages or the likemounted on the boards can be visually observed through the openings. Onthe other hand, there is a demand that the production number or modelnumber of a package, such as a package for constituting a controller,should be protected from visual observation. However, according to theconventional structure of the electronic apparatus, it is difficult tosatisfy this demand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of an appearanceconfiguration of an electronic apparatus according to a firstembodiment;

FIG. 2 is a sectional view illustrating an example of an internalconfiguration of the electronic apparatus according to the firstembodiment;

FIG. 3 is an exploded perspective view illustrating an example of theelectronic apparatus according to the first embodiment;

FIG. 4 is an exploded perspective view illustrating an example of aboard assembly according to the first embodiment;

FIG. 5 is a sectional view schematically illustrating an example of thearrangement position of a controller package according to the firstembodiment;

FIG. 6 is a side view schematically illustrating an example of therelation between the positions of ventilation holes and the position ofthe board assembly, according to the first embodiment;

FIG. 7 is a side view schematically illustrating an example of therelation between the positions of ventilation holes and the position ofthe board assembly, according to the first embodiment;

FIG. 8 is a side view schematically illustrating an example of therelation between the positions of ventilation holes and the position ofthe board assembly, according to a comparative example;

FIGS. 9A and 9B are sectional views illustrating an example of aninternal configuration of an electronic apparatus according to a secondembodiment;

FIG. 10 is an exploded perspective view illustrating an example of theelectronic apparatus according to the second embodiment;

FIG. 11 is an exploded perspective view illustrating an example of aboard assembly according to the second embodiment;

FIGS. 12A and 12B are perspective views illustrating an example offrames according to the second embodiment;

FIGS. 13A to 13C are top views illustrating examples of a ventilationmechanism of a frame according to the second embodiment;

FIG. 14 is a perspective view illustrating another example of theventilation mechanism of a frame according to the second embodiment;

FIGS. 15A to 15E are views illustrating an example of an assemblingsequence of the board assembly according to the second embodiment;

FIGS. 16A and 16B are views illustrating an example of the cover of ahousing according to a third embodiment;

FIG. 17 is a sectional view illustrating another example of the cover ofthe housing according to the third embodiment;

FIG. 18 is a perspective view illustrating an example of a boardassembly according to the third embodiment; and

FIG. 19 is a perspective view illustrating a configuration example of aspacer according to the third embodiment.

DETAILED DESCRIPTION

According to one embodiment, an electronic apparatus includes a printedcircuit board including a plurality of devices that include anonvolatile memory package and a controller package configured tocontrol the nonvolatile memory package, and a housing accommodating theprinted circuit board. The housing includes an opening on a surfaceconstituting the housing. An encryption device among the plurality ofdevices is present in a first region. The first region is a region onthe printed circuit board that is not irradiated with light emitted froma light source placed at the opening. The encryption device is a deviceused for an encryption process of data to be stored into the nonvolatilememory package.

Exemplary embodiments of an electronic apparatus will be explained belowin detail with reference to the accompanying drawings. The presentinvention is not limited to the following embodiments.

First Embodiment

FIG. 1 is a perspective view illustrating an example of an appearanceconfiguration of an electronic apparatus according to a firstembodiment. FIG. 2 is a sectional view illustrating an example of aninternal configuration of the electronic apparatus according to thefirst embodiment. FIG. 3 is an exploded perspective view illustrating anexample of the electronic apparatus according to the first embodiment.FIG. 4 is an exploded perspective view illustrating an example of aboard assembly according to the first embodiment. Hereinafter, theelectronic apparatus will be exemplified by a Solid State Drive (SSD)that uses a nonvolatile memory as a storage medium. Further,hereinafter, for the sake of convenience, it is assumed that thelatitudinal direction of the rectangular top surface or bottom surfaceof the electronic apparatus is an X-direction, its longitudinaldirection is a Y-direction, and its thickness direction is aZ-direction. Furthermore, hereinafter, the relative positional relationsof components arranged in the Z-direction, i.e., their relations in thevertical direction, will be illustrated, by using the arrangement stateof the electronic apparatus illustrated in FIGS. 1 and 2 as a reference.

The electronic apparatus 1 has a flat rectangular parallelepiped shapeas its physical appearance. The electronic apparatus 1 includes ahousing 10 having a hollow rectangular parallelepiped shape, and a boardassembly 20 including one or more boards accommodated in the housing 10.

The housing 10 includes a base 11 and a cover 12. The base 11 includes abottom wall 111 like a flat plate, and side walls 112 a and 112 bperpendicularly extending upward in the Z-direction from the outerperiphery of the bottom wall 111. In this example, the base 11 isprovided with a pair of side walls 112 a each having a surfaceperpendicular to the X-direction, and a single side wall 112 b arrangedat one end in the Y-direction and having a surface perpendicular to theY-direction.

The side walls 112 a are provided with screw holes 113 extending in theZ-direction. The thickness of the side walls 112 a is set larger at theportions formed with the screw holes 113 than at the other portions. Inthis example, the screw holes 113 are arranged near the both ends andnear the center in the Y-direction.

Further, the side walls 112 a are provided with a plurality of pins 114.The pins 114 are disposed on the side walls 112 a and projected upwardin the Z-direction (i.e., toward the cover 12). In this example, thepins 114 are arranged at two places near the screw holes 113 provided onthe side walls 112 a. The pins 114 are provided to perform positioningin the X-direction and Y-direction to the cover 12 with respect to thebase 11 at the time of placing the cover 12 onto the base 11.Accordingly, the cover 12 is provided with through holes 125 forinserting the pins 114 therein, at the corresponding positions.

The bottom wall 111 of the base 11 is provided with screw holes 115. Thescrew holes 115 are provided to fix the board assembly 20 to the base 11by fasteners, such as screws 142. Further, the bottom wall 111 of thebase 11 is provided with a pin (not illustrated). The pin is disposed onthe bottom wall 111 and projected upward in the Z-direction. The pin maybe disposed on a pedestal (not illustrated) provided on the bottom wall111. The pin is provided to perform positioning in the X-direction andY-direction to the board assembly 20 with respect to the base 11.Accordingly, a printed circuit board 21A to be arranged at the lowermostside is provided with a through hole 213 for inserting this pin therein,at the corresponding position.

The cover 12 includes a top wall 121 like a flat plate, and side walls122 perpendicularly extending downward in the Z-direction from the outerperiphery of the top wall 121. In this example, the cover 12 is providedwith a pair of side walls 122 each having a surface perpendicular to theY-direction. Further, the side walls 122 are provided with ventilationholes 123 for cooling, which allow air to flow between the outside andinside of the housing 10.

Heat conductive sheets 131 serving as heat conductive members areprovided at predetermined positions on the bottom wall 111 of the base11 and the top wall 121 of the cover 12. Each heat conductive sheet 131is made of silicone resin, for example, and has thermally conductive andelectrically insulating properties, as well as an elastic property. Eachheat conductive sheet 131 is provided to conduct heat generated by adevice on the board assembly 20 to the base 11 or cover 12, to suppressa temperature rise inside the housing 10. Accordingly, the heatconductive sheets 131 are arranged to be in contact with devices on theupper surface of the board assembly 20 and the top wall 121 of the cover12, and to be in contact with devices on the lower surface of the boardassembly 20 and the bottom wall 111 of the base 11.

The cover 12 is provided with through holes 124 for inserting screws 141therein, and the through holes 125 for inserting the pins 114 therein.The through holes 124 for inserting the screws 141 are arranged at thepositions corresponding to the screw holes 113 of the base 11. Thethrough holes 125 for inserting the pins 114 are arranged at thepositions corresponding to the pins 114 of the base 11. Further, anameplate label 151 with information, such as the model number of theelectronic apparatus 1, described therein is stuck to the upper surfaceof the cover 12.

The base 11 and the cover 12, which constitute the housing 10, are madeof aluminum die cast or the like superior in heat radiation property.

The board assembly 20 includes one or more printed circuit boards as theboards. When the board assembly 20 includes one printed circuit board,the printed circuit board is fixed to the housing 10 by fasteners.Further, when the board assembly 20 includes a plurality of printedcircuit boards, the board assembly 20 further includes one or morespacers, and the printed circuit boards and the spacers are alternatelystacked in the Z-direction, and are fixed by fasteners. In this example,the board assembly 20 has a structure in which three printed circuitboards 21A, 21B, and 21C and two spacers 22A and 22B are alternatelystacked in the Z-direction.

On the respective printed circuit boards 21A to 21C, devices aremounted. The devices are circuit components, which include nonvolatilememory packages 23 a, volatile memory packages 23 b, a controllerpackage 23 c, and capacitors 23 d. Each nonvolatile memory package 23 ahas a configuration such that a nonvolatile semiconductor memory chipusing a NAND type flash memory, for example, is packaged by heatresistant resin, ceramics, or the like. Each volatile memory package 23b has a configuration such that a Dynamic Random Access Memory (DRAM)chip or a Static RAM (SRAM) chip is packaged by heat resistant resin,ceramics, or the like. The controller package 23 c has a configurationsuch that a controller chip for controlling the nonvolatile memorypackages 23 a and the volatile memory packages 23 b is packaged by heatresistant resin, ceramics, or the like. The controller package 23 c isformed of a System-on-a-Chip (SoC), for example. Each capacitor 23 dplays a role to assist the supply of power supplied from a hostapparatus to which the electronic apparatus 1 is connected.

The controller package 23 c serves to control the exchange of data withthe host apparatus. Specifically, upon receiving a data write commandfrom the host apparatus, the controller package 23 c temporarily storesdata to be written, into a write buffer provided in the volatile memorypackages 23 b, and writes the data stored in the write buffer into theposition corresponding to a specified address inside the nonvolatilememory packages 23 a. Further, upon receiving a data read command fromthe host apparatus, the controller package 23 c reads data from theposition corresponding to a specified address inside the nonvolatilememory packages 23 a, and temporarily stores the read data into a readbuffer provided in the volatile memory packages 23 b. Then, thecontroller package 23 c sends the data stored in the read buffer to thehost apparatus.

Further, the controller package 23 c includes a function of encryptingdata to be written at the time of writing the data into the nonvolatilememory packages 23 a, and a function of decrypting the encrypted data atthe time of reading the data from the nonvolatile memory packages 23 a.When the controller package 23 c performs the encryption process anddecrypting process of this kind (which will be simply referred to as“encryption process”) by itself, the controller package 23 c isconsidered as an encryption module (encryption device). On the otherhand, when another package is used in addition to the controller package23 c to perform the encryption process, such that, for example, data tobe treated by the encryption process is read into the volatile memorypackages 23 b to perform the encryption process, each of the packagesassociated with the encryption process is considered as the encryptionmodule. Alternatively, when a dedicated hardware, such as a dedicatedcircuit, is used to perform the encryption process, without using thecontroller package 23 c, the dedicated hardware is considered as theencryption module.

Each device is mounted on at least one of the two main surfaces of eachof the printed circuit boards 21A to 21C by, for example, surfacemounting or the like. In this example, the controller package 23 c isarranged on the lower surface of the lowermost printed circuit board21A, and the volatile memory packages 23 b and the capacitors 23 d arearranged on the upper surface of the lowermost printed circuit board21A. Further, the nonvolatile memory packages 23 a are arranged on theupper surface and lower surface of each of the printed circuit boards21A to 21C.

In addition to the devices, the printed circuit boards 21A to 21C areprovided with board-to-board connectors 24 that mutually andelectrically connect the individual printed circuit boards stacked inthe Z-direction. The board-to-board connectors 24 are mounted on therespective printed circuit boards 21A to 21C by surface mounting. Theboard-to-board connectors 24 are arranged at positions that are oppositeto each other when the printed circuit boards 21A to 21C are superposedin an aligned state. The board-to-board connectors 24 include a femaletype connector 24 a as one type and a male type connector 24 b as theother type, which can be mutually fitted to achieve electricalconnection between the printed circuit boards 21A to 21C. Thus, when theprinted circuit boards 21A to 21C are mutually connected by theboard-to-board connectors 24, the printed circuit boards 21A to 21C arerelatively firmly connected to each other.

The printed circuit board 21A arranged at the lowermost side is providedwith the female type connector 24 a on the upper surface. The printedcircuit board 21C arranged at the uppermost side is provided with themale type connector 24 b on the lower surface. The printed circuit board21B arranged at the middle is provided with the male type connector 24 bon the lower surface, and the female type connector 24 a on the uppersurface. Further, the lowermost printed circuit board 21A is providedwith a connector 25 at one end in the Y-direction, such that theconnector 25 is to be electrically connected to the host apparatuspresent outside. As the standard of the connector 25, for example,Peripheral Component Interconnect express (PCIe™) or Serial AttachedSmall Computer System Interface (SAS) is used.

The printed circuit boards 21A to 21C are provided with through holes212 for inserting the screws 142 that fix the board assembly 20 to thebase 11. These through holes 212 are arranged corresponding to the screwholes 115 of the bottom wall 111 of the base 11. Further, the printedcircuit board 21A arranged at the lowermost side is provided with thethrough hole 213 corresponding to the pin provided on the bottom wall111 of the base 11. Further, the printed circuit boards 21A and 21B areprovided with through holes 214 corresponding to pins 226 provided onthe spacers 22A and 22B described later.

Each of the spacers 22A and 22B is interposed between two of the printedcircuit boards 21A to 21C mutually adjacent in the Z-direction. Each ofthe spacers 22A and 22B holds a state where two of the printed circuitboards 21A to 21C mutually adjacent in the Z-direction have apredetermined interval therebetween. Further, each of the spacers 22Aand 22B includes a function of making it difficult for devices arrangedbetween two of the printed circuit boards 21A to 21C mutually adjacentin the Z-direction to be visually observed, through the ventilationholes 123. Each of the spacers 22A and 22B includes a frame part 221,which has almost the same dimensions as those of the printed circuitboards 21A to 21C and has almost the same outline as that of the printedcircuit boards 21A to 21C, and a reinforcing part 222 or reinforcingparts 222 a and 222 b, which suppress deformation of the frame part 221caused by an external force. The frame part 221 is provided with aplurality of engaging portions 223 of a snap fit type at predeterminedpositions. The plurality of engaging portions 223 are preferablyarranged opposite to each other. In the example illustrated in FIG. 4 ,the engaging portions 223 are arranged on respective ones of a pair oflong sides of the frame part 221, and are opposite to each other.

Each engaging portion 223 includes a cantilever projected downward fromthe frame part 221 at a predetermined position, and a protrusionprovided at the distal end of the cantilever and projected toward theinside of the frame part 221. On the other hand, the printed circuitboards 21A and 21B are provided with cutouts 211 at the positionscorresponding to the engaging portions 223, such that each cutout 211 isrecessed by the thickness of the cantilever.

The frame part 221 is provided with through holes 225 for inserting thescrews that fix the board assembly 20 to the base 11. Further, the framepart 221 is provided with a plurality of pins 226 projected downward.The pins 226 are used to perform positioning in the X-direction andY-direction with respect to each of the printed circuit boards 21A and21B to be fitted. Accordingly, the printed circuit boards 21A and 21Bare provided with through holes 214 for fitting the pins 226 therein, atthe corresponding positions.

In assembling, first, the printed circuit board 21A or 21B is put closerto the lower side of the spacer 22A or 22B. Then, while the positions ofthe through holes 214 of the printed circuit board 21A or 21B are setaligned with the positions of the pins 226 of the spacer 22A or 22B, theprinted circuit board 21A or 21B is brought into contact with the spacer22A or 22B. This results in a state where the protrusions of theengaging portions 223 are positioned on the lower surface side of theprinted circuit board 21A or 21B, and engage with this lower surface. Inthis way, the printed circuit boards 21A and 21B are fixed to thespacers 22A and 22B.

The reinforcing parts 222, 222 a, and 222 b are arranged at anypositions. For example, in the upper side spacer 22B in FIG. 4 , thereinforcing part 222 is provided by connecting the opposite long sidesalmost in parallel with the short sides constituting the frame part 221.Further, in the lower side spacer 22A in FIG. 4 , the first reinforcingpart 222 a is provided by connecting the opposite long sides almost inparallel with the short sides constituting the frame part 221, and thesecond reinforcing part 222 b is provided by connecting the firstreinforcing part 222 a to one of a pair of the short sides almost inparallel with the long sides constituting the frame part 221. The secondreinforcing part 222 b is arranged to extend along the backside of thearrangement position of the controller package 23 c.

The second reinforcing part 222 b is provided with a raised portion 224projected downward. In this example, the raised portion 224 is arrangedwithin the arrangement position of the controller package 23 c on thelowermost printed circuit board 21A. Between the raised portion 224 andthe lowermost printed circuit board 21A, a heat conductive sheet 131 isinterposed. The raised portion 224 has a height to come into contactwith the heat conductive sheet 131 provided on the upper surface of thelowermost printed circuit board 21A. Consequently, heat generated by anoperation of the controller package 23 c mounted on the lower surface ofthe printed circuit board 21A is conducted to the upper surface of theprinted circuit board 21A, and is further conducted to the spacer 22Athrough the heat conductive sheet 131. Then, the heat is released by airflows coming from the ventilation holes 123, i.e., openings. Further, asdescribed above, the controller package 23 c on the lower surface of theprinted circuit board 21A is connected to the bottom wall 111 of thebase 11 through a heat conductive sheet 131. Accordingly, heat generatedby the controller package 23 c is conducted also to the base 11 throughthe heat conductive sheet 131, and is released.

Further, in this example, between a portion of the second reinforcingpart 222 b which is above the arrangement position of the raised portion224 and the nonvolatile memory packages 23 a which is on the lowersurface of the printed circuit board 21B, a heat conductive sheet 131 isinterposed in contact with the both sides. Consequently, heat generatedby the nonvolatile memory packages 23 a is conducted to the spacer 22Athrough the heat conductive sheet 131, and is released by air flowscoming from the ventilation holes 123.

The dimensions of the spacers 22A and 22B in the Z-direction are setsuch that devices mounted on the printed circuit boards 21A to 21C to bearranged above and below the spacers 22A and 22B do not interfere witheach other.

The spacers 22A and 22B are made of an electrically insulating materialthat will not be thermally deformed by a temperature rise due to anoperation of the controller package 23 c and so forth, and that is highin resistance to impact shock and high in thermally conductive property.For example, the spacers 22A and 22B are made of polycarbonate resin.

Here, in the above example, each of the reinforcing parts 222 and 222 ais provided by connecting a pair of opposite sides of the frame part221; however, the embodiment is not limited to this. For example, eachof the reinforcing parts 222 and 222 a may be provided by connecting twosides of the frame part 221 that are not opposite to each other.

Next, with reference to FIGS. 3 and 4 , an explanation will be given ofa method of assembling such an electronic apparatus 1. First, asillustrated in FIG. 4 , the board assembly 20 is assembled with theprinted circuit boards 21A to 21C and the spacers 22A and 22B.Specifically, while the through holes 214 of the printed circuit boards21A and 21B and the pins 226 of the spacers 22A and 22B are set alignedwith each other, the printed circuit boards 21A and 21B and the spacers22A and 22B are put closer to each other in the Z-direction, and arefixed by the engaging portions 223 of the spacers 22A and 22B. In theillustrated example, the lowermost printed circuit board 21A and thespacer 22A are fixed to each other, and the middle printed circuit board21B and the spacer 22B are fixed to each other. Then, the printedcircuit boards 21A to 21C adjacent in the Z-direction are connected toeach other by the board-to-board connectors 24. Consequently, the boardassembly 20 is constructed in which the printed circuit boards 21A to21C and the spacers 22A and 22B are alternately arranged in theZ-direction.

Then, as illustrated in FIG. 3 , the electronic apparatus 1 isassembled. First, the heat conductive sheets 131 are stuck to the base11 and the cover 12 at predetermined positions. Thereafter, while thethrough hole 213 of the lowermost printed circuit board 21A constitutingthe board assembly 20 is set aligned with the pin (not illustrated)ofthe base 11, the board assembly 20 is placed on the base 11. Then, theboard assembly 20 is fixed to the base 11 by fasteners, such as thescrews 142. Specifically, in this fixing, the screws 142 are set to passthrough the through holes 212 of the printed circuit boards 21A to 21Cconstituting the board assembly 20 and the screw-insertion through holes225 of the spacers 22A and 22B, and to reach the screw holes 115 of thebase 11.

Thereafter, while the through holes 125 of the cover 12 are set alignedwith the pins 114 provided on the side walls 112 a of the base 11, thecover 12 is placed on the base 11. Then, the cover 12 is fixed to thebase 11 by fasteners, such as the screws 141. Specifically, in thisfixing, the screws 141 are set to pass through the through holes 124provided on the cover 12, and to reach the screw holes 113 provided onthe side walls of the base 11. Then, the nameplate label 151 is stuck tothe upper surface of the cover 12, and thereby the electronic apparatus1 is assembled.

Next, an explanation will be given of the ventilation holes 123 providedon the electronic apparatus 1 that accommodates the board assembly 20.FIG. 5 is a sectional view schematically illustrating an example of thearrangement position of the controller package according to the firstembodiment. For the sake of convenience in explanation, FIG. 5illustrates a sectional view including one end in the Y-direction at aposition where the connector 25 is not present. In FIG. 5 , theconstituent elements corresponding to those described above are denotedby the same reference symbols.

The housing 10 includes a side wall 122 formed with the ventilationholes 123 and arranged at one end in Y-direction. Now, it is assumedthat, at the ventilation holes 123 of this side walls 122, artificiallight sources 100 are placed to irradiate light (visible light) of whicha wavelength is 400 nm to 750 nm. In FIG. 5 , optical paths at outeredges of light emitted from each ventilation hole 123 are schematicallyillustrated by arrows, and the range of light emitted from eachventilation hole 123 is schematically illustrated by hatching of linesoblique downward to the left. This hatching is shown between the opticalpaths at two outer edges of light emitted from each ventilation hole123.

In this case, an encryption module, i.e., the controller package 23 c inthis example, is arranged at a position where the light does not reach.For example, when it is assumed that, of the upper surface and lowersurface of the board assembly 20, a light unreachable region is a firstregion and a light reachable region is a second region, the controllerpackage 23 c is arranged in the first region. Here, the upper surfaceand lower surface of the board assembly 20 within the range illustratedin FIG. 5 are the first region.

As described above, as the spacers 22A and 22B are interposed betweenthe printed circuit boards 21A to 21C stacked in the Z-direction,devices arranged in the spaces between the printed circuit boards 21A to21C cannot be visually observed through the ventilation holes 123.Further, as the controller package 23 c, which is considered as theencryption module, is present in the first region, the encryption module(controller package 23 c) is prevented from being visually observedthrough the ventilation holes 123. Thus, in relation to the encryptionmodule (for example, the controller package 23 c), it is possible toprevent the production number, model number, design information (such aswire trace and internal structure), or assembling information from beingvisually observed through the ventilation holes 123.

Here, an explanation of the arrangement positions of the ventilationholes 123 in the Z-direction relative to the board assembly 20, whichare set to prevent the encryption module from being visually observed,will be given. In the following examples, there are a case (A) where theencryption modules are arranged on both of the upper and lower surfacesof the board assembly 20; a case (B) where the encryption module isarranged on one of the upper and lower surfaces of the board assembly20; and a case (C) where no encryption module is arranged on either ofthe upper and lower surfaces of the board assembly 20. Further, in thefollowing examples, the encryption modules include the controllerpackage 23 c and the nonvolatile memory packages 23 a.

In the case (A) where the encryption modules are arranged on both of theupper and lower surfaces of the board assembly 20:

In this case, as illustrated in FIG. 5 , within an arrangement positionrange R₀ of the board assembly 20 in the Z-direction, the ventilationholes 123 provided on the housing 10 are arranged within a range R₁,which is between the upper surface and lower surface of the boardassembly 20. This is to prevent light from reaching the upper surfaceand lower surface of the board assembly 20 when the artificial lightsources 100 are placed at the ventilation holes 123. Consequently, theupper surface and lower surface of the board assembly 20 become thelight unreachable first region. Thus, the nonvolatile memory packages 23a on the upper surface of the board assembly 20 and the controllerpackage 23 c on the lower surface of the board assembly 20 are arrangedin the light unreachable first region.

In the case (B) where the encryption module is arranged on one of theupper and lower surfaces of the board assembly 20:

FIG. 6 is a side view schematically illustrating an example of therelation between the positions of the ventilation holes and the positionof the board assembly, according to the first embodiment. FIG. 6illustrates a case where the encryption module is arranged on the lowersurface of the board assembly 20, for example. In this case, theventilation holes 123 provided on the housing 10 are arranged within arange R₁ between the lower surface of the board assembly 20 and the topwall 121 of the cover 12. Accordingly, as long as this condition issatisfied, the ventilation holes 123 may be arranged also above theuppermost position of the arrangement position range R₀ of the boardassembly 20 in the Z-direction.

In the example of FIG. 6 , the upper surface of the board assembly 20 isthe second region to be irradiated with light, and the lower surface ofthe board assembly 20 is the first region not to be irradiated withlight. In this case, as the encryption module is not arranged on theupper surface side of the board assembly 20, the encryption module isprevented from being visually observed even if the upper surface of theboard assembly 20 is irradiated with light from the artificial lightsources 100 placed at the ventilation holes 123. On the other hand, asthe ventilation holes 123 are not arranged below the lowermost positionof the arrangement position range R₀ of the board assembly 20 in theZ-direction, the lower surface of the board assembly 20 will never beirradiated with light from the artificial light sources 100 placed atthe ventilation holes 123.

Here, FIG. 6 illustrates a case where the encryption module is arrangedon the lower surface of the board assembly 20. On the other hand, wherethe encryption module is arranged on the upper surface of the boardassembly 20, the positional relations described above in the verticaldirection become reverse to those illustrated in FIG. 6 .

Further, if an alteration of firmware for controlling an operation ofthe electronic apparatus 1 can cause a problem in security, theencryption module including, for example, the nonvolatile memorypackages 23 a that store the firmware is preferably arranged at aposition not to be visually observed.

In the case (C) where no encryption module is arranged on either of theupper and lower surfaces of the board assembly 20:

FIG. 7 is a side view schematically illustrating an example of therelation between the positions of ventilation holes and the position ofthe board assembly, according to the first embodiment. FIG. 7illustrates a case where no encryption module is arranged on either ofthe upper and lower surfaces of the board assembly 20, for example. Inthis case, the ventilation holes 123 provided on the housing 10 arearranged at any positions within a range R₁, which is between the topwall 121 of the cover 12 and the bottom wall 111 of the base 11,regardless of the arrangement position range R₀ of the board assembly 20in the Z-direction. In other words, the ventilation holes 123 may bearranged also above the uppermost position of the arrangement positionrange R₀ of the board assembly 20 in the Z-direction, or the ventilationholes 123 may be arranged also below the lowermost position of thearrangement position range R₀ of the board assembly 20 in theZ-direction.

In the example of FIG. 7 , the upper surface and lower surface of theboard assembly 20 become the second region to be irradiated with light.In this case, as the encryption module is not arranged on either of theupper surface side and lower surface side of the board assembly 20, theencryption module is prevented from being visually observed even if theupper surface and lower surface of the board assembly 20 are irradiatedwith light from the artificial light sources 100 placed at theventilation holes 123.

Further, in this case, the encryption module results in being arrangedin a region surrounded by the spacers 22A and 22B of the board assembly20. In the region surrounded by the spacers 22A and 22B, the encryptionmodule will never be irradiated with light from the artificial lightsources 100 placed at the ventilation holes 123. In the example of FIG.7 , the controller package 23 c is arranged on the upper surface of thelowermost printed circuit board 21A.

Further, if an alteration of firmware for controlling an operation ofthe electronic apparatus 1 can cause a problem in security, theencryption module including, for example, the nonvolatile memorypackages 23 a that store the firmware is preferably arranged at aposition not to be visually observed.

As a comparative example, an explanation will be given of thearrangement positions of the ventilation holes 123 in the Z-directionrelative to the board assembly 20, in a case where the encryptionmodules are arranged on both of the upper and lower surfaces of theboard assembly 20, and the encryption modules can be visually observedthrough the ventilation holes 123. FIG. 8 is a side view schematicallyillustrating an example of the relation between the positions of theventilation holes and the position of the board assembly, according tothe comparative example. FIG. 8 illustrates a case where the encryptionmodules are arranged on both of the upper and lower surfaces of theboard assembly 20, for example.

As illustrated in FIG. 8 , the ventilation holes 123 provided on thehousing 10 are arranged also below the lowermost position of thearrangement position range R₀ of the board assembly 20 in theZ-direction, and arranged also above the uppermost position of the same.When the artificial light sources 100 are placed at the ventilationholes 123, the upper surface or lower surface of the board assembly 20comes to include a portion to be irradiated with light. In the exampleof FIG. 8 , the upper surface and lower surface of the board assembly 20become the second region to be irradiated with light. When theencryption module is present in the second region, the encryption modulecan be visually observed through the ventilation holes 123. Further, asthe spacers 22A and 22B are not provided between the printed circuitboards 21A to 21C adjacent in the Z-direction, the encryption modulearranged between the printed circuit boards 21A to 21C adjacent in theZ-direction ends up being irradiated with light. In other words, theencryption module can be visually observed through the ventilation holes123. Accordingly, from the viewpoint to prevent the encryption modulefrom being visually observed, the arrangement of the ventilation holes123 described above is inapposite.

Here, in the above description, it is designed to prevent the entiretyof the encryption module from being visually observed. However, forexample, where information to be protected from visual observation isthe production number, model number, design information (such as wiretrace and internal structure), or assembling information of theencryption module, it may be designed to allow part of the encryptionmodule, such as its lateral surface, to be visually observed, as long asthe information described above cannot be visually observed.

Further, the above description is exemplified by a case where the boardassembly 20 accommodated in the housing 10 includes the three printedcircuit boards 21A to 21C; however, the embodiment is not limited tothis. The board assembly 20 may include one or more printed circuitboards.

Further, the above description is exemplified by a case where thespacers 22A and 22B respectively fix the printed circuit boards 21A and21B positioned below by the engaging portions 223; however, theembodiment is not limited to this. The spacers 22A and 22B mayrespectively fix the printed circuit boards 21B and 21C positioned aboveby engaging portions 223.

Further, the above description is exemplified by a case where theventilation holes 123 are provided on the side walls 122 of the cover12; however, the ventilation holes 123 may be provided on the side walls112 a and 112 b of the base 11. Further, the ventilation holes 123 areformed in a mesh shape on the side walls 122; however, the ventilationholes 123 may be formed in another shape, such as a slit or latticeshape.

Further, the above description is exemplified by a case where theventilation holes 123 are provided on the side walls 122 of the cover12; however, the embodiment may be applied to a case where theventilation holes 123 are provided on the bottom wall 111, top wall 121,or another side wall of the housing 10, for example.

Further, the above description is exemplified by a case where thecontroller package 23 c is considered as the encryption module or thecontroller package 23 c and nonvolatile memory packages 23 a areconsidered as the encryption modules. However, where data to be treatedin an encryption process is read into volatile memory packages 23 b toperform the encryption process, these volatile memory packages 23 b arealso included in the encryption modules. The arrangement positions ofthe volatile memory packages 23 b on the upper surface or lower surfaceof the board assembly 20 may be achieved by the same method as thatdescribed above.

In the first embodiment, between the printed circuit boards 21A to 21Cadjacent in the Z-direction, the spacers 22A and 22B are interposedwhich are formed in a frame shape having almost the same outline as thatof the printed circuit boards 21A to 21C. In this state, the printedcircuit boards 21A to 21C and the spacers 22A and 22B are fixed to eachother to form the board assembly 20, which is then accommodated in thehousing 10 including the side walls 122 formed with the ventilationholes 123. Here, the controller package 23 c is present in the firstregion of the board assembly 20 that is light unreachable when the boardassembly 20 is irradiated with light from the artificial light sources100 placed at the ventilation holes 123. Consequently, it is possible toprevent the controller package 23 c from being visually observed fromoutside the housing 10.

In other words, it is designed to prevent the production number, modelnumber, design information, such as wire trace and internal connection,or assembling information of the controller package 23 c in theelectronic apparatus 1 from being visually observed from outside thehousing 10. As a result, it is possible to improve the reliability ofthe electronic apparatus 1 concerning its security.

Further, as the spacers 22A and 22B are made of a resin superior in heatradiation property, there is also an effect capable of releasing heatgenerated in the printed circuit boards 21A to 21C adjacent in theZ-direction. Further, the reinforcing parts 222, 222 a, and 222 b of thespacers 22A and 22B are provided with the raised portions 224, and theheat conductive sheets 131 are interposed between the raised portions224 and the printed circuit boards 21A to 21C or devices mounted on theprinted circuit boards 21A to 21C. Consequently, it is possible toconduct heat from the printed circuit boards 21A to 21C to the spacers22A and 22B, and to release the heat by air flows from the ventilationholes 123 provided on the housing 10.

Further, the spacers 22A and 22B are provided with the pins 226 forpositioning, and the printed circuit boards 21A and 21B are providedwith through holes 214 at the positions corresponding to the pins.Consequently, by inserting the pins 226 of the spacers 22A and 22B intothe through holes 214 of the printed circuit boards 21A and 21B, theprinted circuit boards 21A and 21B can be easily attached to the spacers22A and 22B in a state where the alignment therebetween has beenachieved. Further, as the spacers 22A and 22B are provided with theengaging portions 223 of a snap fit type, the printed circuit boards 21Aand 21B can be firmly fixed.

Second Embodiment

In the first embodiment, each spacer arranged between printed circuitboards adjacent in the thickness direction has a structure thatsurrounds the space between the printed circuit boards, and does notallow air coming from outside to flow into the space between the printedcircuit boards. In the second embodiment, an explanation will be givenof an electronic apparatus having a structure that allows air fromoutside to flow also into the space between printed circuit boardsadjacent in the thickness direction.

FIGS. 9A and 9B are sectional views illustrating an example of aninternal configuration of an electronic apparatus according to thesecond embodiment. FIG. 9A is a sectional view in a directionperpendicular to the latitudinal direction. FIG. 9B is a sectional viewin a direction perpendicular to the longitudinal direction. FIG. 10 isan exploded perspective view illustrating an example of the electronicapparatus according to the second embodiment. FIG. 11 is an explodedperspective view illustrating an example of a board assembly accordingto the second embodiment. FIGS. 12A and 12B are perspective viewsillustrating an example of frames according to the second embodiment.FIGS. 13A to 13C are top views illustrating examples of a ventilationmechanism of a frame according to the second embodiment. FIG. 14 is aperspective view illustrating another example of the ventilationmechanism of a frame according to the second embodiment. FIGS. 15A to15E are views illustrating an example of an assembling sequence of theboard assembly according to the second embodiment. Hereinafter, theelectronic apparatus will be exemplified by an SSD, as in the firstembodiment. Further, hereinafter, for the sake of convenience, it isassumed that the latitudinal direction of the rectangular top surface orbottom surface of the electronic apparatus 1 is an X-direction, itslongitudinal direction is a Y-direction, and its thickness direction isa Z-direction. Further, hereinafter, the relative positional relationsof components arranged in the Z-direction, i.e., their relations in thevertical direction, will be illustrated, by using as a reference thearrangement state of the electronic apparatus 1 illustrated in FIGS. 9A,9B, and 10 . Furthermore, hereinafter, an explanation of structuresdifferent from those of the first embodiment will be given, while noexplanation of structures the same as those of the first embodiment willbe given.

As illustrated in FIGS. 9A, 9B, and 10 , in the electronic apparatus 1according to the second embodiment, a housing 10 has the same structureas that of the first embodiment, and a pair of side walls 122perpendicular to the Y-direction are provided with ventilation holes 123for cooling, which allow air to flow between the outside and inside ofthe housing 10.

In the electronic apparatus 1 according to the second embodiment, aboard assembly 20 includes a plurality of printed circuit boards and oneor more spacers. The printed circuit boards and the spacers arealternately stacked in the Z-direction, and are fixed by fasteners. Inthis example, the board assembly 20 has a structure in which threeprinted circuit boards 21A, 21B, and 21C and two spacers 27A and 27B arealternately stacked in the Z-direction. Further, the board assembly 20includes electrically insulating sheets 29 interposed between theprinted circuit boards 21A and 21B adjacent in the Z-direction andbetween the printed circuit boards 21B and 21C adjacent in theZ-direction.

Each of the printed circuit boards 21A to 21C has a structure the sameas that described in the first embodiment. However, in the firstembodiment, the printed circuit boards 21A to 21C are electricallyconnected to each other by the board-to-board connectors 24; on theother hand, in the second embodiment, the printed circuit boards 21A to21C are electrically connected to each other by flexible printedcircuits (Flexible Printed Circuits, each of which will be referred toas “FPC”) 26A and 26B.

As illustrated in FIG. 11 , the printed circuit board 21A is arranged atthe middle, the printed circuit board 21B is arranged at one side (leftside in FIG. 11 ) of the printed circuit board 21A in the X-direction,and the printed circuit board 21C is arranged at the other side (rightside in FIG. 11 ) of the printed circuit board 21A in the X-direction.The FPCs 26A and 26B each for electrically connecting two printedcircuit boards are provided between the printed circuit boards 21A and21B and between the printed circuit boards 21A and 21C. Each of the FPCs26A and 26B is composed of a base layer made of a flexible andelectrically insulating material and an electrically conductive layermade of an electrically conductive material bonded thereon. As the baselayer, polyimide, polyethylene terephthalate, polyethylene naphthalate,or the like is used. As the electrically conductive layer, copper or thelike is used. The electrically conductive layer is to be connected tothe wiring layer of each printed circuit board.

In this example, the FPCs 26A and 26B are arranged at long sides of theprinted circuit boards 21A to 21C. Further, the lengths of FPCs 26A and26B have been determined in accordance with the stacking order of theprinted circuit boards 21A to 21C. In this example, as the printedcircuit board 21A, the printed circuit board 21B, and the printedcircuit board 21C are to be stacked in this order from below, the lengthof the FPC 26B that connects the printed circuit boards 21A and 21C toeach other is set larger than the length of the FPC 26A that connectsthe printed circuit boards 21A and 21B to each other.

Each of the spacers 27A and 27B is interposed between the two printedcircuit boards 21A and 21B or two printed circuit boards 21B and 21Cadjacent in the Z-direction. Each of the spacers 27A and 27B holds astate where the two printed circuit boards 21A and 21B or two printedcircuit boards 21B and 21C adjacent in the Z-direction have apredetermined interval therebetween. Further, each of the spacers 27Aand 27B includes a function of making it difficult for devices arrangedbetween the two printed circuit boards 21A and 21B or two printedcircuit boards 21B and 21C adjacent in the Z-direction to be visuallyobserved, through the ventilation holes 123. Further, each of thespacers 27A and 27B includes a function of guiding part of the air flowsfrom the ventilation holes 123 at one side of the housing 10 to theventilation holes 123 at the other side, through the space between thetwo printed circuit boards 21A and 21B or two printed circuit boards 21Band 21C adjacent in the Z-direction.

As illustrated in FIGS. 12A and 12B, each of the spacers 27A and 27Bincludes a frame part 271, which has almost the same outline as that ofthe printed circuit boards 21A to 21C. The frame part 271 is providedwith a plurality of engaging portions 273 of a snap fit type atpredetermined positions. In the example of FIGS. 12A and 12B, theengaging portions 273 are arranged on respective ones of the upper andlower sides of the frame part 271 in the Z-direction. Consequently, eachof the spacers 27A and 27B comes to be fixed to two of the printedcircuit boards 21A to 21C, which are arranged above and below this oneof the spacers 27A and 27B in the Z-direction. Here, when the spacers27A and 27B are seen in a state placed by the same orientation, thespacer 27A is provided with the engaging portions 273 on a long side atone side, and the spacer 27B is provided with the engaging portions 273on a long side at the other side. The engaging portions 273 arepreferably arranged at positions that prevent the printed circuit boards21B and 21C from being opened up by a reaction force of the FPCs 26A and26B when the board assembly 20 is assembled. Further, as illustrated inFIG. 15A, in accordance with the positions of the engaging portions 273,the printed circuit boards 21B and 21C are provided with recessedportions 217 on long sides opposite to the long sides provided with theFPCs 26A and 26B. When the printed circuit boards 21B and 21C are fixedto the spacers 27A and 27B, the engaging portions 273 engage with therecessed portions 217; thus, the printed circuit boards 21B and 21C arefixed, and are prevented from being opened up by a reaction force of theFPCs 26A and 26B.

The frame part 271 is provided with through holes 275 for inserting thescrews 142 that fix the board assembly 20 to the base 11. Further, theframe part 271 is provided with a plurality of pins 276 projecteddownward and upward. The pins 276 are used to perform positioning in theX-direction and Y-direction with respect to each of the printed circuitboards 21A and 21B to be fitted. Accordingly, the printed circuit boards21A to 21C are provided with through holes 214 for fitting the pins 276therein, at the corresponding positions.

As illustrated in FIG. 11 , in assembling, first, the spacers 27A and27B are respectively put closer to the upper sides of the printedcircuit boards 21A and 21B. Then, while the positions of the pins 276 ofthe spacers 27A and 27B are set aligned with the positions of thethrough holes 214 of the printed circuit boards 21A and 21B, the spacers27A and 27B are respectively brought into contact with the printedcircuit boards 21A and 21B. This results in a state where theprotrusions of the engaging portions 273 are positioned on the lowersurface sides of the printed circuit boards 21A and 21B, and engage withthese lower surfaces. Further, the printed circuit boards 21B and 21Care respectively put closer to the upper sides of the spacers 27A and27B. Then, while the positions of the through holes 214 of the printedcircuit boards 21B and 21C are set aligned with the positions of thepins 276 of the spacers 27A and 27B, the printed circuit boards 21B and21C are respectively brought into contact with the spacers 27A and 27B.This results in a state where the protrusions of the engaging portions273 are positioned on the upper surface sides of the printed circuitboards 21B and 21C, and engage with these upper surfaces. In this way,the printed circuit boards 21A to 21C are fixed to the spacers 27A and27B.

As illustrated in FIGS. 12A and 12B, the side surface 271 a of the framepart 271 to be opposite to the ventilation holes 123 is provided with aventilation mechanism. The ventilation mechanism is configured such thatslits are formed in the side surface 271 a of the frame part 271. Asillustrated in FIG. 12A, two types of slits 2711 and 2712 different indirection are alternately formed in the side surface 271 a along theX-direction. As a result, wall portions 2715 a and 2715 b, each of whichhas a pentagonal shape with an apex protrusive in the Y-direction, areformed at places surrounded by the two types of slits 2711 and 2712. Thepentagonal wall portions 2715 a and 2715 b adjacent in the X-directionhave different apex directions, that is, one of them is toward apositive direction side in the Y-direction and the other is toward anegative direction side in the Y-direction.

Further, as illustrated in FIGS. 9A and 11 , the spacer 27A is arrangedon the lower side in the Z-direction. Further, the printed circuit board21A is arranged below the spacer 27A in the Z-direction, and capacitors23 d are arranged at one end of the printed circuit board 21A in theY-direction. The capacitors 23 d are present outside a side surface 271b of the frame part 271. The two capacitors 23 d present in theX-direction serve to block the field of vision into the board assembly20. Accordingly, as illustrated in FIG. 12A, the side surface 271 b ofspacer 27A is structured such that no side surface portion is formed atthe positions where the capacitors 23 d are to be arranged, but onepentagonal wall portion 2715 a is formed to be present between the twocapacitors 23 d.

On the other hand, in the spacer 27B arranged on the upper side in theZ-direction, as illustrated in FIG. 12B, the side surfaces 271 a and 271b to be opposite to the ventilation holes 123 are provided withpentagonal wall portions 2715 a and 2715 b.

As illustrated in FIGS. 13A to 13C, it is assumed that, when the sidesurfaces 271 a and 271 b are seen in the Y-direction, the distancebetween the mutually adjacent ends of the pentagonal wall portions 2715a and 2715 b is denoted by “d”. The distance between the mutuallyadjacent ends of the pentagonal wall portions 2715 a and 2715 b ispreferably set to be zero as illustrated in FIG. 13A, i.e., there shouldbe no gap between the mutually adjacent ends of the pentagonal wallportions 2715 a and 2715 b. Alternatively, the distance between themutually adjacent ends of the pentagonal wall portions 2715 a and 2715 bis preferably set to be negative, i.e., there should be a partialoverlap near the mutually adjacent ends of the pentagonal wall portions2715 a and 2715 b. With this arrangement, as described in the firstembodiment, it is possible to prevent the encryption module in the boardassembly 20 from being visually observed through the ventilation holes123 of the housing 10. However, as the ventilation holes 123 provided onthe side walls 122 of the housing 10 are formed in a mesh shape, the netportions between the ventilation holes 123 overlap with the slits of theside surface 271 a of the frame part 271, and make it difficult for theencryption module inside to be visually observed. Accordingly, asillustrated in FIG. 13C, it may be designed to leave a gap of about 0.1to 0.2 mm between the mutually adjacent pentagonal wall portions 2715 aand 2715 b. If the distance “d” between the mutually adjacent ends ofthe pentagonal wall portions 2715 a and 2715 b is larger than 0.2 mm, itmay become possible for the encryption module inside to be visuallyobserved. Thus, the distance “d” is preferably set to be up to 0.2 mm.

Here, the slits 2711 and 2712 provided on the spacers 27A and 27B are amere example, and another structure may be provided instead. Forexample, as illustrated in FIG. 14 , slits 2712 may be formed inparallel with each other on the side surface 271 a or side surface 271 bof the frame part 271 along the X-direction. In this case, wall portions2715 c, each of which has a parallelogram shape, are formed at placessurrounded by respective sets of mutually adjacent two slits 2712. Thedistance between the mutually adjacent ends of the parallelogram wallportions 2715 c also satisfies the relation described with reference toFIGS. 13A to 13C. Other than this, a slit structure which allows air toflow through the inside of the board assembly 20 and makes it difficultfor the inside to be visually observed may be used. Further, forexample, the spacers 27A and 27B are made of polycarbonate resin.

The electrically insulating sheets 29 are interposed between the printedcircuit boards 21A to 21C mutually adjacent in the Z-direction. Theelectrically insulating sheets 29 serve to prevent devices on theprinted circuit boards 21A to 21C mutually adjacent in the Z-directionfrom being damaged by coming into contact with each other, and to relaximpact shock when the electronic apparatus 1 receives the impact shock.Further, each electrically insulating sheet 29 includes a function ofelectrically insulating the portion between two of the printed circuitboards 21A to 21C mutually adjacent.

Next, with reference to FIGS. 15A to 15E, an explanation of a method ofassembling such the electronic apparatus 1 will be given. However, sincea method of fixing the board assembly 20 to the housing 10 to assemblethe electronic apparatus 1 is the same as that described in the firstembodiment, its description will be omitted; thus, a method ofassembling the board assembly 20 by using the printed circuit boards 21Ato 21C, the spacers 27A and 27B, and the electrically insulating sheets29 will be described.

Here, as illustrated in FIG. 15A, a group 21 of the printed circuitboards connected by the FPCs 26A and 26B is placed in an unfolded state.In this example, in a state where the connector 25 of the printedcircuit board 21A is present on the upper side in FIG. 15A, the printedcircuit board 21B is present at the left side of the printed circuitboard 21A next to the FPC 26A, and the printed circuit board 21C ispresent at the right side of the printed circuit board 21A next to theFPC 26B.

Then, as illustrated in FIG. 15B, while the pins (not illustrated) onthe lower side of the spacer 27A are set aligned with the through holes214 of the printed circuit board 21A at the middle, the spacer 27A isput closer to the printed circuit board 21A from above in theZ-direction. Then, the spacer 27A is fixed to the printed circuit board21A by the engaging portion 273 on the lower side of the spacer 27A.

Thereafter, the electrically insulating sheet 29 (not illustrated) isplaced on the printed circuit board 21A with the spacer 27A attachedthereon. Then, as illustrated in FIG. 15C, the printed circuit board 21Bis folded back above the printed circuit board 21A. At this time, whilethe through holes 214 of the printed circuit board 21B are set alignedwith the pins 276 on the upper side of the spacer 27A, the printedcircuit board 21B is put closer to the spacer 27A from above in theZ-direction. Then, the printed circuit board 21B is fixed to the spacer27A by the engaging portion 273 on the upper side of the spacer 27A.

Then, as illustrated in FIG. 15D, while the pins (not illustrated) onthe lower side of the spacer 27B are set aligned with the through holes214 of the printed circuit board 21B, the spacer 27B is put closer tothe printed circuit board 21B from above in the Z-direction. Then, thespacer 27B is fixed to the printed circuit board 21B by the engagingportion 273 on the lower side of the spacer 27B.

Thereafter, the electrically insulating sheet 29 (not illustrated) isplaced on the printed circuit board 21B with the spacer 27B attachedthereon. Then, as illustrated in FIG. 15E, the printed circuit board 21Cis folded back above the printed circuit board 21B. At this time, whilethe through holes 214 of the printed circuit board 21C are set alignedwith the pins 276 on the upper side of the spacer 27B, the printedcircuit board 21C is put closer to the spacer 27B from above in theZ-direction. Then, the printed circuit board 21C is fixed to the spacer27B by the engaging portion 273 on the upper side of the spacer 27B. Asa result, the board assembly 20 is constructed.

Here, in the second embodiment, the board assembly 20 is assembled byusing the group 21 of the printed circuit boards in which the printedcircuit boards 21A to 21C are mutually connected by the FPCs 26A and26B. However, the spacers 27A and 27B including the slits describedabove may be used for a board assembly 20 having a structure in whichthe printed circuit boards 21A to 21C are connected to each other by theboard-to-board connectors 24 described in the first embodiment. Further,also in the second embodiment, the relation between the positions of theventilation holes 123 of the housing 10 and the arrangement position ofthe encryption module in the board assembly 20 satisfies the relationdescribed in the first embodiment.

In the second embodiment, between the printed circuit boards 21A to 21Cadjacent in the Z-direction, the spacers 27A and 27B are interposedwhich have almost the same outline as that of the printed circuit boards21A to 21C. The spacers 27A and 27B include the side surfaces 271 a and271 b formed with the slits and being opposite to the ventilation holes123 of the housing 10. In this state, the printed circuit boards 21A to21C and the spacers 27A and 27B are set to form the board assembly 20,which is then accommodated in the housing 10. Consequently, air flowsfrom the ventilation holes 123 of the housing 10, through the slits onone side of the spacers 27A and 27B, also into the board assembly 20,and is exhausted from the slits on the other side. Thus, there is aneffect capable of improving the cooling effect on devices that generateheat inside the board assembly 20. Particularly, there is a case wherethe controller package 23 c, which is formed of the SoC and is large inheat generation, is attached to the lower surface, in the Z-direction,of the printed circuit board 21A. In this case, heat is conducted alsoto the upper surface, in the Z-direction, of the printed circuit board21A, at the position where the controller package 23 c is attached.Accordingly, when air flows along the Y-direction through the slits ofthe spacer 27A, the back side at the position where the controllerpackage 23 c is attached is cooled by air.

Further, when the side walls 122 of the housing 10 provided with theventilation holes 123 are seen in the Y-direction, the net portions ofthe housing 10 overlap with the slits of the spacers 27A and 27B. Thismakes it difficult for the inside of the board assembly 20 to bevisually observed through the slits. Further, when the ends of wallportions of the spacers 27A and 27B provided at positions opposite tothe ventilation holes 123 are set to overlap with each other, the insideof the board assembly 20 can be prevented from being visually observedthrough the slits, when seen in the Y-direction. Consequently, it ispossible to improve the reliability of the electronic apparatus 1concerning its security.

Third Embodiment

In the first and second embodiments, the ventilation hole provided onthe housing are formed in a mesh shape, and the side surfaces or thelike of the board assembly, as long as no encryption module is on them,can be visually observed through the ventilation holes. In the thirdembodiment, an explanation of an electronic apparatus that does notallow the inside of the housing to be visually observed through theventilation holes provided on the housing will be given.

FIGS. 16A and 16B are views illustrating an example of the cover of ahousing according to a third embodiment. FIG. 16A is a perspective view,and FIG. 16B is a sectional view. FIG. 17 is a sectional viewillustrating another example of the cover of the housing according tothe third embodiment. FIG. 18 is a perspective view illustrating anexample of a board assembly according to the third embodiment. FIG. 19is a perspective view illustrating a configuration example of a spaceraccording to the third embodiment.

In the third embodiment, as illustrated in FIGS. 16A and 16B, eachventilation hole 123 formed on the side walls 122 of the cover 12 isprovided with a recessed portion 1221 formed by louver working. Therecessed portion 1221 is formed with its lower end and both ends in theX-direction continued to the surface of the corresponding side wall 122,and formed with an inclined surface bent toward the inside of thehousing 10 and extending upward within the range of the correspondingventilation hole 123. The position of the upper end of the recessedportion 1221 is almost the same as the position of the upper end of thecorresponding ventilation hole 123. In other words, the recessed portion1221 is arranged to substantially cover the corresponding ventilationhole 123 from visual observation on the housing 10 in the Y-direction.Accordingly, when the housing 10 is visually observed in theY-direction, the inside of the housing 10 is prevented from beingvisually observed. Here, FIGS. 16A and 16B illustrate a structure inwhich the recessed portion 1221 is formed on the lower end side of thecorresponding ventilation hole 123, and causes air to flow upward.However, this is a mere example, and the recessed portion 1221 may beformed at the corresponding ventilation hole 123 to cause air to flowsideward or downward.

Further, as illustrated in FIG. 17 , each ventilation hole 123 formed onthe side walls 122 of the cover 12 may be provided with a cut-and-raisedportion 1222 formed by press working. The cut-and-raised portion 1222 isformed with its lower end continued to the surface of the correspondingside wall 122, and formed with an inclined surface present on the innerside of the housing 10 and extending upward within the range of thecorresponding ventilation hole 123. The position of the upper end of thecut-and-raised portion 1222 is almost the same as the position of theupper end of the corresponding ventilation hole 123. In other words, thecut-and-raised portion 1222 is arranged so that it can cover thecorresponding ventilation hole 123 when the housing 10 is visuallyobserved in the Y-direction. Here, FIG. 17 illustrates a structure inwhich the cut-and-raised portion 1222 is formed on the lower end side ofeach ventilation hole 123, and causes air to flow upward. However, thisis a mere example, and the cut-and-raised portion 1222 may be formed ateach ventilation hole 123 to cause air to flow sideward or downward.

As described above, each ventilation hole 123 on the side walls 122 ofthe housing 10 is provided with a blindfold, such as the recessedportion 1221 or cut-and-raised portion 1222, not to allow the inside ofthe housing 10 to be visually observed. Consequently, it is possible toimprove the reliability of the electronic apparatus 1 concerning itssecurity. Here, as a spacer used for the board assembly 20 according tothe third embodiment, either one of the spacers described in the firstand second embodiments can be used; furthermore, a spacer which does nothave a structure described in the first and second embodiments, whichprevents the encryption module from being visually observed fromoutside, may be used. As illustrated in FIG. 18 , it is sufficient ifspacers 28A and 28B have a structure that can hold a state where theprinted circuit boards 21A to 21C adjacent in the Z-direction havepredetermined intervals therebetween.

Each of the spacers 28A and 28B has almost the same dimensions as thoseof the printed circuit boards 21A to 21C, and has almost the sameoutline as that of the printed circuit boards 21A to 21C, which issubstantially rectangular. As illustrated in FIG. 19 , each of thespacers 28A and 28B includes column members 281 arranged near the fourcorners to maintain, at a predetermined interval therebetween, two ofthe printed circuit boards 21A to 21C mutually adjacent in theZ-direction, and beam members 282 connecting the column members 281 toeach other. In the third embodiment, the thickness of each beam member282 in the Z-direction is set smaller than that of each column member281. Accordingly, when the board assembly 20 has been assembled, gapsare formed as passages of air flow between the printed circuit boards21A to 21C adjacent in the Z-direction.

The beam members 282 are provided with a plurality of engaging portions283 of a snap fit type at predetermined positions. In the example ofFIG. 19 , the engaging portions 283 are arranged on respective ones ofthe upper and lower sides in the Z-direction. Consequently, each of thespacers 28A and 28B comes to be fixed to two of the printed circuitboards 21A to 21C, which are arranged above and below this one of thespacers 28A and 28B in the Z-direction. Here, as in the secondembodiment, it may be designed such that, when the spacers 28A and 28Bare seen in a state placed by the same orientation, the spacer 28A isprovided with the engaging portions 283 on a long side at one side, andthe spacer 28B is provided with the engaging portions 283 on a long sideat the other side. In a case where the FPCs 26A and 26B form theconnection between the printed circuit boards 21A and 21B and theconnection between the printed circuit boards 21B and 21C, as in thesecond embodiment, the engaging portions 283 are preferably arranged atpositions that prevent the printed circuit boards 21B and 21C from beingopened up by a reaction force of the FPCs 26A and 26B when the boardassembly 20 is assembled. Further, as illustrated in FIG. 15A, inaccordance with the positions of the engaging portions 283, the printedcircuit boards 21B and 21C are provided with recessed portions 217 onlong sides opposite to the long sides provided with the FPCs 26A and26B. When the printed circuit boards 21B and 21C are fixed to thespacers 28A and 28B, the engaging portions 283 engage with the recessedportions 217; thus, the printed circuit boards 21B and 21C are fixed,and are prevented from being opened up by a reaction force of the FPCs26A and 26B.

The column members 281 are provided with through holes 285 for insertingthe screws 142 that fix board assembly 20 to the base 11. Further, thecolumn members 281 are provided with a plurality of pins 286 projecteddownward and upward. The pins 286 are used to perform positioning in theX-direction and Y-direction with respect to each of the printed circuitboards 21A to 21C to be fitted. Accordingly, the printed circuit boards21A to 21C are provided with through holes 214 for fitting the pins 286therein, at the corresponding positions.

Here, the constituent elements corresponding to those of the first andsecond embodiments are denoted by the same reference symbols, and theirdescription will be omitted. Further, as a method of assembling theelectronic apparatus 1 according to the third embodiment, the samemethod as that described in the first or second embodiment may be used.Further, also in the third embodiment, the arrangement position of theencryption module in the board assembly 20 is set at a position thatcannot be visually observed through the ventilation holes 123 of thehousing 10, as in the first embodiment.

In the third embodiment, each ventilation hole 123 of the housing 10 isprovided with a blindfold. Consequently, even though the ventilationmechanism is provided, it is possible to prevent the inside of thehousing 10 from being visually observed. Further, as a structure of thehousing 10 is used to prevent the inside of the housing 10 from beingvisually observed, it is possible to determine the arrangement positionof the encryption module in the board assembly 20 inside the housing 10and the arrangement positions of the ventilation holes 123, withoutsuffering from the restriction described in the first embodiment.Further, for the board assembly 20, a spacer can be used which does nothave a structure for preventing an encryption module from being visuallyobserved from outside. In this case, it is possible to further improveflows of air into the board assembly 20.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A memory system comprising: a first printedcircuit board having a first main surface and a second main surface, thesecond main surface opposing the first main surface; a nonvolatilememory; a first encryption device mounted on the first main surface, thefirst encryption device being configured to encrypt data to be stored inthe nonvolatile memory; and a housing including a wall and a firstplate, the wall being perpendicular to the first plate, the first platebeing parallel to the first printed circuit board, the housingaccommodating the first printed circuit board, the nonvolatile memory,and the first encryption device, the wall including a first region and asecond region, the first region including an opening, the second regionincluding no opening, the first plate having a first surface, the firstsurface facing the first main surface of the first printed circuitboard, wherein the second region of the wall is bounded by a firstposition and a second position, the first position being a positionwhere the wall is intersected by an imaginary extension of the firstmain surface of the first printed circuit board, and the second positionbeing a position where the wall is intersected by an imaginary extensionof the first surface of the first plate.
 2. The memory system accordingto claim 1, wherein the first encryption device is not irradiated withlight emitted from a light source if the light source is placed at theopening.
 3. The memory system according to claim 2, further comprising:a second printed circuit board having a third main surface and a fourthmain surface, the fourth main surface opposing the third main surface,the third main surface facing the second main surface of the firstprinted circuit board; and a second encryption device mounted on thefourth main surface, the second encryption device being configured toencrypt data to be stored in the nonvolatile memory, wherein the housingfurther accommodates the second printed circuit board and the secondencryption device, the housing further includes a second plate having asecond surface, the second surface facing the fourth main surface of thesecond printed circuit board, the wall further includes a third region,the third region including no opening, wherein the third region isbounded by a third position and a fourth position, the third positionbeing a position where the wall is intersected by an imaginary extensionof the fourth main surface of the second printed circuit board, thefourth position being a position where the wall is intersected by animaginary extension of the second surface of the second plate, and thesecond encryption device is not irradiated with light emitted from thelight source if the light source is placed at the opening.
 4. The memorysystem according to claim 3, further comprising: a third encryptiondevice mounted on the second main surface of the first printed circuitboard, the third encryption device being configured to encrypt data tobe stored in the nonvolatile memory; and a spacer interposed between thefirst printed circuit board and the second printed circuit board, a partof the spacer being located between the opening and the third encryptiondevice, wherein a side of the part of the spacer facing the opening isirradiated with light emitted from the light source if the light sourceis placed at the opening, and the third encryption device is notirradiated with light emitted from the light source if the light sourceis placed at the opening.
 5. The memory system according to claim 4,wherein the spacer includes a slit configured to allow air to flow fromthe opening into a region that is surrounded by the first printedcircuit board, the second printed circuit board, and the spacer.
 6. Thememory system according to claim 1, wherein the housing has arectangular parallelepiped shape.
 7. The memory system according toclaim 4, wherein the wall is further perpendicular to the second plate.8. The memory system according to claim 1, wherein the first encryptiondevice and the first surface of the first plate are respectively incontact with both sides of a heat conductive member that is placedbetween the first encryption device and the first plate.
 9. The memorysystem according to claim 1, wherein the first encryption deviceincludes a controller package, the controller package accommodating acontroller chip configured to control the nonvolatile memory.
 10. Thememory system according to claim 4, wherein each of the first encryptiondevice, the second encryption device, and the third encryption deviceincludes one of a controller package, a volatile memory package, and anonvolatile memory package, the controller package accommodating acontroller chip configured to control the nonvolatile memory, thevolatile memory package accommodating a volatile memory chip, thenonvolatile memory package accommodating a nonvolatile memory chip. 11.A memory system comprising: a first printed circuit board having a firstmain surface and a second main surface, the second main surface opposingthe first main surface; a second printed circuit board having a thirdmain surface and a fourth main surface, the fourth main surface opposingthe third main surface, the third main surface facing the second mainsurface of the first printed circuit board; a spacer interposed betweenthe first printed circuit board and the second printed circuit board,the spacer including a first part and a second part, a gap between thefirst part and the second part forming a first slit; a nonvolatilememory; an encryption device mounted on the second main surface of thefirst printed circuit board, the encryption device being configured toencrypt data to be stored in the nonvolatile memory; and a housingincluding a first wall, the first wall being perpendicular to the firstprinted circuit board and the second printed circuit board, the housingaccommodating the first printed circuit board, the second printedcircuit board, the spacer, the nonvolatile memory, and the encryptiondevice, the first wall including at least one first opening, wherein thefirst part of the spacer and the second part of the spacer locatebetween the first opening and the encryption device, and the first partof the spacer or the second part of the spacer is placed such that thefirst part of the spacer or the second part of the spacer blocks lightemitted from a light source not to irradiate the encryption device ifthe light source is placed at the first opening.
 12. The memory systemaccording to claim 11, wherein the first slit of the spacer isconfigured to allow air to flow from the first opening into a regionthat is surrounded by the first printed circuit board, the secondprinted circuit board, and the spacer.
 13. The memory system accordingto claim 12, wherein the housing further includes a second wall facingthe first wall, the second wall including a second opening, the spacerfurther includes a third part and a fourth part respectively facing thefirst part and the second part, a gap between the third part and thefourth part forming a second slit, the third part and the fourth partbeing located between the second opening and the encryption device, andthe second slit of the spacer is configured to allow air flowed from thefirst opening into the region to flow out through the second opening.14. The memory system according to claim 11, wherein the at least onefirst opening comprises a plurality of first openings, the first wallincludes a mesh-shaped portion, the mesh-shaped portion forming theplurality of first openings, and a net portion of the mesh-shapedportion between two adjacent first openings overlaps the first slit ofthe spacer when seen in a direction perpendicular to the first wall. 15.The memory system according to claim 11, wherein the first part of thespacer and the second part of the spacer are formed with no distancetherebetween when seen in a direction perpendicular to the first wall.16. The memory system according to claim 11, wherein the first part ofthe spacer and the second part of the spacer are formed with a distancetherebetween when seen in a direction perpendicular to the first wall.17. The memory system according to claim 11, wherein at least one of thefirst part of the spacer and the second part of the spacer has apolygonal shape when seen in a first direction, the first directionbeing parallel to the first wall.
 18. The memory system according toclaim 17, wherein an apex having the largest angle among angles of thepolygonal-shaped first part of the spacer protrudes in a seconddirection, the second direction being perpendicular to the first wall,and an apex having the largest angle among angles of thepolygonal-shaped second part of the spacer protrudes in a thirddirection, the third direction being perpendicular to the first wall andopposite to the second direction.
 19. The memory system according toclaim 17, wherein the polygonal shape is a pentagon.
 20. The memorysystem according to claim 11, wherein the encryption device includes oneof a controller package, a volatile memory package, and a nonvolatilememory package, the controller package accommodating a controller chipconfigured to control the nonvolatile memory, the volatile memorypackage accommodating a volatile memory chip, the nonvolatile memorypackage accommodating a nonvolatile memory chip.